1. Field of the Invention
The present invention relates generally to a semiconductor device manufacturing apparatus and method, and in particular to a semiconductor device manufacturing apparatus and method capable of suppressing laser trimming problems.
2. Discussion of the Background Art
Laser trimming is a well known method of cutting one of fuse elements formed on a semiconductor wafer substrate fuses are cut at an appropriate position with a laser beam in order to adjust an electric performance of a semiconductor device having an analog circuit. Cutting is performed before division of a semiconductor wafer substrate into a plurality of chips, as discussed in Japanese Patent Application Laid Open No. 2000-323576.
A constant voltage generation circuit and a voltage detection circuit are typical examples of such an analog circuit.
FIG. 14 illustrates a semiconductor device including a constant voltage generation circuit 81 that stably supplies power from a direct current power source 77 to a load 79. The constant voltage generation circuit 81 includes an input terminal Vbat 83 to which the direct current power supply 77 is connected, a reference voltage generation circuit 85, an operational amplifier 87, a P-channel type MOS transistor 89 (hereinafter referred to as a PMOS) constituting an output driver, a voltage divider formed by a pair of division resistances R1 and R2, and an output terminal Vout 91.
In the operational amplifier 87, an output terminal is connected to a gate electrode of the PMOS 89. A reference voltage Vref is applied from the reference voltage generation circuit 85 to an inversion input terminal. A voltage obtained by dividing an output voltage Vout with the pair of resistances R1 and R2 is applied to a non-inversion input terminal. The voltage is thus controlled to equal the reference voltage Vref.
Another semiconductor device including a voltage detection circuit 93 is illustrated in FIG. 15. As shown in the voltage detection circuit 93, an operational amplifier 87 is provided, and a reference voltage generation circuit 85 is connected to an inversion input terminal to receive a reference voltage Vref. A terminal voltage to be measured from an input terminal Vsens 95 is divided by the voltage divider R1 and R2 and is input to a non-inversion input terminal of the operational amplifier 87. The operational amplifier 87 then outputs a signal via an output terminal 97.
In the voltage detection circuit 93, when the terminal voltage to be measured is high, and accordingly, a voltage divided by the voltage divider R1 and R2 is higher than the reference voltage Vref, an output of the operational amplifier 87 maintains a high level. In contrast, when the terminal voltage to be measured descends and accordingly, a voltage divided by the voltage divider R1 and R2 is lower than the reference voltage Vref, an output of the operational amplifier 87 becomes low.
In general, since a reference voltage Vref transmitted from a reference voltage generation circuit varies from chip to chip due to imprecision in a manufacturing process for the constant voltage generation circuit of FIG. 14 and the voltage detection circuit of FIG. 15, tunable division resistances are utilized to change and adjust a resistance value by cutting fuse elements at an appropriate position in order to adjust for the imprecision.
FIG. 16 illustrates still another semiconductor device including a circuit having tunable division resistances for adjusting a resistance value. As shown, a resistance element Rbottom, m+1 items of resistance elements RT0 to RTm, and a resistance element Rtop are serially connected, wherein the sign “m” represents a positive integer. To the resistance elements RT0 to Rtm, fuse elements RL0 to RLm are connected in parallel, respectively, as discussed in Japanese Patent Application Laid Open No. 2000-150799.
When a faulty division resistance unbalances a resistance ratio between a pair of resistances, in order to increase a manufacturing precision in a manufacturing process, corrections are made using a tunable resistance circuit formed from units of a resistance element and a fuse element serially connected and arranged in a ladder. Such a division resistance is corrected by optionally cutting one of fuse elements RL0 to RLm with a laser beam. Accordingly, a prescribed serial resistance value can be obtained between a NodeM, between the resistance elements Rtop and RTm, and a NodeL, between the resistance elements Rbottom and RT0.
When the tunable resistances of FIG. 16 are applied to the voltage divider R1 and R2 of the constant voltage generation circuit of FIG. 14, an end of the resistance element Rbottom is grounded, an end of the resistance element Rtop is connected to a drain of PMOS89, and a terminal NodeL is connected to a non-inversion input terminal of the operational amplifier 87, for example. Otherwise, an end of the resistance element Rbottom is grounded, an end of the resistance element Rtop is connected to the drain of the PMOS89, and the terminal NodeM is connected to the non-inversion input terminal of the operational amplifier 87.
Further, when the tunable resistances of FIG. 16 are applied to the voltage divider R1 and R2 of the voltage detection circuit of FIG. 15, an end of the resistance element Rbottom is grounded, an end of the resistance element Rtop is connected to an input terminal 95, and a terminal NodeL is connected to the non-inversion input terminal of the operational amplifier 87, for example. Otherwise, an end of the resistance element Rbottom is grounded, an end of the resistance element Rtop is connected to the direct current power source 77, and the terminal NodeM is connected to the non-inversion input terminal of the operational amplifier 87.
However, various problems are raised when the fuse element is cut by irradiation with a laser beam. Specifically, a laser trimming apparatus irradiating the laser beam is expensive. A running cost of the laser trimming apparatus is high. A peripheral protection film and a substrate film of the fuse element are damaged by the laser beam. In addition, a fuse element material or the like scatters around an opening section when the fuse is being melted.